Two identical cylindrical vessels with their bases at the  same level each contains a liquid of density d. The height of the liquid in one vessel is h₁ and that in the other vessel is h_2. The area of either base is A. The work done by gravity in equalising the levels, when the two vessels are connected is:

• A

  $({\mathrm{h}}_1~{\mathrm{h}}_2)\mathrm{gd}$

• B

  $({\mathrm{h}}_1~ {\mathrm{h}}_2)\mathrm{gAd}$

• C

  $\left(1/2\right){({\mathrm{h}}_1~{\mathrm{h}}_2)}^2\mathrm{gAd}$

• D

  $\left(1/4\right)({\mathrm{h}}_1~{\mathrm{h}}_2)\mathrm{gAd}$